The present invention relates to self-leveling silicone sealant compositions and methods for making such compositions. More particularly, the present invention relates to one component, acyloxy-functional, room temperature vulcanizable (RTV) silicone compositions which incorporate therein, as a self-leveling agent, an amine such as, for example, n-hexylamine.
In many applications, it is desirable to utilize a self-leveling silicone sealant composition. Traditionally, self-leveling, one component silicone RTV's are manufactured using untreated fumed silica fillers. The manufacturing process for producing these self-leveling compositions requires extremely high shear mixing conditions as well as elevated temperatures for effecting the mixing.
Accordingly, it would be highly desirable to provide self-leveling, one component silicone RTV's which can use both treated and untreated silica fillers and eliminates the need for high shear mixing at elevated temperatures in their manufacture.
Bruner, U.S. Pat. No. 3,035,016, discloses room temperature vulcanizable silicone compositions of the formula ##STR1## where Ac is a saturated aliphatic monoacyl radical of a carboxylic acid, R and R.sup.1 are selected from the group consisting of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals, and n is an integer of at least five. The acyloxy-functional polysiloxane is prepared by reacting acyloxy silanes of the formula R.sup.1 Si(OAc).sub.3, with hydroxylated siloxanes of the formula ##STR2## where R and R.sup.1 are as previously defined.
Bruner, U. S. Pat. No. 3,077,465, teaches that the room temperature vulcanizable composition described in U.S. Pat. No. 3, 035,016 can be made to cure more effectively by including therein from 0.001 to 10 percent by weight of a carboxylic acid salt of a metal ranging from lead to manganese, inclusive, in the electromotive series of metals.
Ceyzeriat, U.S. Pat. No. 3,133,891, relates to room temperature vulcanizable compositions which comprise a linear diorganopolysiloxane consisting of units of the formula R.sub.2 SiO, in which each R represents a monovalent radical selected from the group consisting of halogenated and halogenfree aliphatic, alicyclic and aromatic hydrocarbon radicals and containing at least 0.1 weight percent hydroxyl groups and 0.5 to 25 weight percent, based on the diorganopolysiloxane, of an organotriacyloxysilane of the formula R.sup.1 Si(OCOR.sup.2).sub.3, where R.sup.1 is a monovalent radical selected from the group consisting of lower alkyl, alkenyl, aryl and aralkyl radicals and R.sup.2 is a monovalent radical selected from the group consisting of alkyl radicals having 1 to 18 carbon atoms and aryl radicals.
Kulpa, U.S. Pat. No. 3,296,161, describes a silicone composition comprising an organopolysiloxane having a viscosity of from about 200 to 500,000 centipoise at 25.degree. C., and containing from 0.02 to 2% silicon-bonded hydroxyl groups; and from 0.2 to 6 parts per 100 parts of said organopolysiloxane of a dialkoxydiacyloxysilane and from 1.8 to 6 parts of an organotriacyloxysilane.
Goossens, U.S. Pat. No. 3,296,195, discloses a silicone RTV composition comprising a silanol chainstopped polydiorganosiloxane, and an alkoxyacyloxysilane wherein the four valences of silicon are satisfied by either zero or one silicon-bonded radical selected from monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals, at least one radical selected from alkoxy radicals and halogenated alkoxy radicals, and at least one saturated aliphatic monoacyl radical.
Beers, U.S. Pat. No. 3,382,205, provides a substantially anhydrous organopolysiloxane composition curable at room temperatures to the elastomeric state upon exposure to moisture comprising (A) 100 parts of a silanol terminated organopolysiloxane consisting essentially of chemically combined diorganosiloxy units of the formula R.sub.2 SiO; (B) 2 to 20 parts of a curing agent of the formula RSi(OCOR.sup.1).sub.3 ; and (C) 2 to 30 parts of an organosilicon process aid composed of diorganosiloxy units of (A) chemically combined with organosiloxy units of the formula RSiO.sub.1.5 and triorganosiloxy units of the formula R.sub.3 SiO.sub.0.5 ; where the organosilicon process aid has from 0.1 to 8 weight percent hydroxy radicals attached to silicon, a ratio of organosiloxy units to diorganosiloxy units of 0.11 to 1.4 and a ratio of triorganosiloxy units to diorganosiloxy units of 0.02 to 1.
Nowhere, however, do any of these references disclose or suggest the inclusion of an amine in order to make the curable compositions self-leveling rather than thixotropic.
All of the foregoing patents are hereby incorporated by reference into the instant disclosure in their entireties for their teachings directed to acyloxy-functional silicone compositions.